f(x) = 3x² + 6x - 1
The graph is a parabola open upward (a= 3>0) with a minimum.
Calculate the vertex:
x = -b/2a → x = -6/(2.3) = -1. Then the axis of symmetry is x = - 1
Now to calculate the minimum, plugin the value of x:
y = 3x² + 6x - 1
y = 3(-1)² + 6(-1) -1
y= 3 - 6 -1 and y = - 4,
Ten the vertex (minimum) is at (-1,- 4)